The goal of this research project is to provide information as to the mechanism of the accelerated progression of large vessel atherosclerosis in diabetes, and to identify the cause(s) of capillary basement membrane abnormalities in diabetic microangiopathy. An in vivo and an in vitro experimental approach will be employed to study two early events in the development of atherosclerosis. Arterial smooth muscle cell proliferation and collagen synthesis will be studies in vivo in arteries of alloxan- or streptozotocin- induced diabetic rabbits made atherosclerotic by dietary cholesterol or by arterial injury in the absence of hyperlipidemia, and in vitro using cultures of diabetic and nondiabetic vascular smooth muscle and endothelial cells to investigate the role of diabetic serum, serum lipoproteins (including VLDL, LDL, HDL and delipidated serum), growth hormone, insulin or glucose on cell proliferation and collagen synthesis by these cells. Collagen production and deposition will be localized by immunofluorescent antibody staining and will be chemically analyzed by slab gel electrophoresis, fluorography, ion exchange and molecular sieve chromatography, in intact diabetic vascular tissues and in cultures of vascular cells. The activity of several important post-ribosomal enzymes that modify the collagen alpha chains, including prolyl hydroylase, glucosyl transferase and lysyl oxidase will be measured to more clearly define the effects of the diabetic state on collagen hydroxylation, glycosylation and cross-linking, respectively. The final objective is to establish the vascular endothelial cell as the source of basement membrane collagen in diabetic microangiopathy by studying collagen synthesis in these cells when grown in vitro under conditions approximating those found in the serum of diabetics.